UPDATE 5: There are reports, which have been confirmed by police, of a man dressed as a police officer opening fire at Utøya in Buskerud. Police are now on-site and have sealed off the area, but there are people hiding from the gunman in the sealed zone, and it is not known how many have been injured, if any.

A gunman detained after shootings at a youth meeting on a Norwegian island and a bombing in central Oslo on Friday is Norwegian, Justice Minister Knut Storberget said.

"Our information is that he is Norwegian," he told a news conference. "I don't know so much about him."

He said that seven people were killed in a bombing in central Oslo and 10 injured. Several people were killed and others wounded in a shooting at a youth camp northwest of Oslo of the ruling Labour Party, he added.